Aircraft steering apparatus



Dec. 3, 1957 J. F. SCHOPPEL AIRCRAFT STEERING APPARATUS Original FiledDec. 8, 1944 3 Sheets-Sheet l KPESUJM O. mun-03m Oh IN V EN TOR. JOHN FSCHOEPPEL AUG-ME) Dec. 3, 1957 J. F. SCHOPPEL ,3

AIRCRAFT STEERING APPARATUS Original Filed Dec. 8, 1944 3 Sheets-Sheet 5FIG. 4

INVENTOR. JQI'N E SOHOEPPEL ATTORAEY United States Patent Ill AIRCRAFTSTEERING APPARATUS John iSchoeppel, Minneapolis, Minn., assignor toMinneapolis-Honeywell Regulator Company, Minneapolis, .Minn., acorporation of Delaware '25 Claims. c1. 74-54 My invention relatesgenerally to control systems and more particularly tosystems having acondition responsive elementand a rebalancing element connected togetherso that an unbalance between the two will cause theoperationof'acondition-controlling means and simultaneously operate therebalancingelement to place the :system in a new :condition of balance.

. This application is a division of co-pending application Serial .No.567,254 filed December 8, 1944, Patent 2,715,709 dated January 20,,1955.

:In operation of airplanes, because of the loading or other unbalance,it is often necessary to make :greater use ofa :controlsurface, such astheelevator, tomaintainthe plane in :a level attitude and on thezsameheading. When there is such an unbalance, if the control surfaceswere instreamlined position, the plane would deviate from thedesiredconditiom-hence the control surfaces must be maintained in adifferent position, and any deviation of the surface from that positioncauses the usual reaction of the plane. This new or balanced positionmust be maintained all the time that the ,plane is .in the properattitude and .on the proper heading, changes being made only when thereis a deviation from these conditions; and this is true whether the planeis being flown by a human or an automatic pilot. Since the unbalance mayvary in direction and .magnitude, though generally remainingsubstantially constant for a, given flight, a properly designedautopilot will have provision for aligning the balanced position of thecontrolsurfaces withthe zero point, or position of no control .signal,of the controlling device. The majority of autopilots usea gyroscope asthe controlling device'to sense any deviation of theplane from itsdesired attitude or heading, .and to originate the proper signalto-operate the control surfaces so as to return .the plane to its properattitude. Means must therefore be provided for aligning the balancedposition of the control surfaces with the zero point of the gyroscope,as previously mentioned; and, depending uponwhetherthe operating meansis electrical, mechanical, or fluid, this aligning means may take theform of resistors, linkages, or valves.

Because of the versatility and precision available with electricalcircuits, their use as a control means has found increasing favor amongpilots. In the hands of an experienced pilot, the electrically operatedautomatic pilot produced results superior -to those of any differentlyoperated means, and-an-example of suchan automatic pilot is shown in theapplication of Willis H. Gille, Serial No. 447,989, filed June 22, 1942.However, one of the disadvantages of an electrically'operated system'hasbeen the somewhat involvedprocedure necessary for a proper adjustment ofthe automatic pilot. Because of the sensitivity and fastresponse of theelectrical system it is necessary that the aligning, or centering, beaccomplished .accurately; and it hasbeen found'tha't many pilots,through inexperience or *inattention, fail'to align the electricalsystern with the physical trim of the airplane, and hence 2,814,954Patented Dec. 3, 1957 "Ice when the autopilot is engaged there is apronounced lurch as the ship assumes a new position.

It is therefore a major object of my invention to provide a :controlsystem which requires less attention and ability on the part of theoperator than systems previously used, but one which nevertheless willprovide a degree and quality of control previously attainable only byskilled operators.

it is another object of my invention to provide a control system whereinoperations which previously had to be performed sequentially and afterproper time delay, are performed automatically without further attentionfrom the operator.

It is also an object of my invention to provide a control system havingautomatic centering or balancing means adapted to balance the systemwhen the apparatus controlled by it is not connected thereto.

it is anobject of my invention to provide a control sys tem which maynot be operated if a malfunction exists or if certain requiredconditions have not been met.

It is a further object of my invention to provide a gyroscope havingcontrol elements connected thereto and means associated therewith tocenter these elements automatically when the gyroscope reaches apredetermined speed.

It is an object of my invention to provide a gyroscope having motormeans to maintain the rotor of the gyroscope normally in a horizontalposition, and having means preventing operation of the motor until the'gyro scope rotor has reached a predetermined speed.

It is another object of my invention to provide a gyro scope which maynot be connected into a control system if its rotor has not reached apredetermined speed.

Still another object of my invention is to provide a balancing meanswhich may be connected so as to furnish a signal opposing the signalfrom a control system, thereby providing a resulting signal which iszero or which diners from zero by a predetermined amount.

These and other objects of my invention will become apparent from thefollowing description of a preferred form thereof and the drawingsillustrating that form, in which:

Figure 1 is a schematic diagram of the alternating current networks usedin my system,

Figure 2 is a schematic diagram of the power and interlock circuit usedin my system,

*Figure 2a is a schematic diagram of a portion of the power diagramshown in Figure 2, and showing amodified embodiment of my invention,

Figure 3 is a detailed schematic diagram of the directional stabilizerand parts associated therewith,

Figure 4 is a view of the gyroscope of the directional stabilizershowingthe action of the torque motor and Figure 5 is a detailed View of thecentering contacts used in conjunction with the directional stabilizer.

Referrng now to the drawings and particularly to Figure ,1 thereof, thenumeral 10 indicates a network ofwseveral bridges containing conditionresponsive .devices ,so arranged that a change in condition, sensed bythem, will be sent as a signal to an amplifier 13 where the signal willbe amplified and used to operate a servo .motor 16 connected by cablesto the ailerons,rnot shown, ,of the ;air plane. A similar network 11connected to amplifier 14 operates servo motor 17 to control the rudder,not shown,

, while an elevator network 12 sends a signal to .an amrespectively, agyroscopically controlled potentiometer 40 consisting of a resistor 41and a wiper 42, a source of power such as a transformer 43 having asecondary winding 44 and a primary winding 45 and a series of fixedresistors 46, 47, 48 and 49. The gyroscope resistor 41 is connectedacross the secondary 44-; and the rebalancing resistor 32 in series withresistors 36 and 37 of centering potentiometers 34 and 35 is connectedin parallel with the gyroscope resistor 41. The upper end of centeringresistor 36 is connected to its wiper 38 so that as the latter is movedback and forth more or less of the resistor 36 is shorted. A similarconnection is made between centering resistor 37 and its wiper 39 andthe two wipers are mechanically connected together and provided withmanually controllable means so that as one of the two resistors hasprogressively more of its resistance shorted, the other resistor hasprogressively less of its resistance shorted. In this way the totalresistance through potentiometers 31, 34, and 35 remains a constant asthe centering potentiometer wipers 33 and 39 are moved from one extremeposition to the other. A shunt connection across rebalancingpotentiometer 31 is provided by resistance 49 which is selectivelyconnected in series with one of three fixed resistors 46, 47, or 48 byswitch 50. The resistors 46, 47 and 43 have different values and arearranged so that a high, medium, or low resistance shunt acrossbalancing potentiometer 31 may be provided.

Above bridge 30 in network 10, as shown in Figure 1, is .a second bridge51 consisting of a banking potentiometer 52 having a center tappedresistor 53 and a wiper 54, an accelerating potentiometer 55 having acenter tapped resistor 56 and a Wiper 57, a compensating potentiometer58 having a resistor 59 and a wiper 60, a pair of resistors 61 and 62,and a source of power, shown as a transformer 63 having a secondarywinding 64 and primary winding 45. The ends of the accelerating resistor56 are connected together and to one terminal of the secondary 64 of thetransformer 63 and the center tap is connected through resistor 61 andresistor 62 to the other terminal of the secondary 64. The wiper 57 ofthe accelerating potentiometer 55 is connected to one end of theresistor 53 of the banking potentiometer 52 and the other end of theresistor 53 is connected through resistor 62 to its terminal of thesecondary 64 of the transformer 63. The center tap of resistor 53 isconnected to the wiper 42 of gyroscope potentiometer 40 and is alsoconnected to one end of resistor 59 of compensating potentiometer 58while the wiper 54 of banking potentiometer 52 is connected to theopposite end of the resistor 59. It will thus be seen that the voltageimpressed across the resistor 53 of the banking poten tiometer 52 willbe dependent upon the position of the wiper 57 of the acceleratingpotentiometer 55, this voltage being a minimum when the wiper is alignedwith the center tap of the potentiometer 55 and a maximum when it is ateither extreme position to one side. Since the ends of the resistor 56of the accelerating potentiometer 55 are connected together there willbe no inversion or shifting of phase as the wiper 57 passes from oneside of the center tap to the other; whereas in potentiometer 52, aswiper 54 moves from one end of resistance 53 to the other, the voltagemeasured between the center tap and the wiper 54 will decrease until azero value is reached when the wiper is in line with the center tap andthen gradually increase, but with a phase shift of 180 degrees, reachinga maximum when the wiper 54 is at the other extreme end of resistor 53.Wiper 57 of accelerating potentiometer 55 and wiper 54 of bankingpotentiometer 52 are mechanically connected together so that both movesimultaneously in the same direction as they leave their centerpositions so that a higher voltage is impressed across resistor 53 and agreater percentage of this total voltage across this resistor appearsbetween the center tap and wiper 54. This voltage will thus vary assomething more than a linear function of the displacement and, becauseof resistances 61 and 62, will be somewhat less than a squared or secondorder function, but will nevertheless be an exponential function 1yingsomewhere in between these two limits.

From wiper 60 connection is made to a bridge 70 which includes a centertapped resistor 71, a balancing potentiometer 72 consisting of aresistor 73 with a wiper 74, a source of power such as a transformer 75having a secondary winding 76 and a primary winding 45. The centertapped resistance 71 is connected across the secondary windings 76 ofthe transformer 75 while the center tap of the resistor is connected tothe wiper 60 of the compensating potentiometer 58; the potentiometer 72is likewise connected across the secondary winding 76 so that theresistors 71 and 73 are in parallel and the voltage signals developed bythe bridge 70 will appear across the center tap of the resistor 71 andthe wiper 74 of the potentiometer 72. From wiper 74 connection is madeto the amplifier 13, which, under certain conditions, drives a balancingmotor 77 to which the wiper 74 is mechanically connected.

The rudder network 11 is similar in many respects to the aileron network10 and consists of three bridges 130, 151, and 170 connected togethersimilarly to bridges 30, 51 and 70. Bridge includes a rebalancingpotentiometer 131 having a resistor 132 and a wiper 133, a pair ofcentering potentiometers 134 and 135 consisting of resistors 136 and 137with wipers 138 and 139, respectively, a gyroscopically operatedpotentiometer 140 consisting of resistor 141 and wiper 142, athreeposition switch 150, and fixed resistors 146, 147, 148 and 149.

The rebalancing potentiometer 131 is connected across the outputterminals of the secondary 144 of a transformer 143, and a seriescircuit, consisting of the centering potentiometer 134, thegyroscopically operated potentiometer 140 and the centeringpotentiometer 135, is connected in parallel with the balancingpotentiometer 132. The wiper 138 is electrically connected to one end ofthe centering potentiometer 134 and the wiper 139 is similarly connectedto one end of the potentiometer 135 so that movement of the wiper shortsa greater or less amount of its associated resistance. The two wipersare mechanically connected together and provided with manual operatingmeans so that as the wipers are moved, the total resistance in theseries circuit consisting of the centering potentiometer 134, thegyroscopically operated potentiometer 140, and the centeringpotentiometer 135, remains a constant. Connected in parallel with thegyroscopically operated potentiometer 140 is a resistance circuitconsisting of fixed resistor 149 connected through switch 159 to one ofthe three fixed resistors 146, 147, or 148, these last three resistorshaving different values so that depending upon the position of switch150, a low, medium, or high resistance circuit is shunted across thepotentiometer 140.

From wiper 142 of the gyroscopically operated potentiometer 140connection is made to a bridge 151 which includes a gyroscopicallyoperated skid potentiometer 152 having a center tapped resistor 153 anda wiper 154, a compensating potentiometer 158 which has a resistor 159and a wiper 160, and a source of power such as a transformer 163 havinga secondary winding 164 and a primary winding 45. The ends of theresistor 153 are connected to the leads from the secondary 164 of thetransformer 163, and the center tap of the resistance is connected tothe wiper 142 of the gyroscopically operated potentiometer 140. Wiper154 of the skid potentiometer 152 is connected to one end of theresistor 159 of the compensating potentiometer 158, while the other endof the resistor is connected to the center tap of the resistor 153 sothat wiper of the compensating potentiometer 158 may be set to receiveany desired percentage of the voltage developed between the center tapand the wiper 154 of the potentiometer 152.

Bridge 170 is similar in all respects to bridge 70 shown in the aileronnetwork and has a center tapped resistor 171, a balancing potentiometer172 consisting of a resistor 173 and a wiper 174, and a transformer 175having a secondary 176 and a primary 45. Center tapped resistor 171 isconnected across the output terminals of thesecondary 176 of thetransformer 175 and the resistor 173 of the centering potentiometer 172is likewise connected across the output terminals of the secondary 176placing it in parallel with center tapped resistance 171. The center tapof resistor 171 is connected to wiper 160 of the compensatingpotentiometer 158, and wiper 174 of balancing potentiometer 172 isconnected to the input of an amplifier 14 which, under certainconditions, will drive a balancing motor 177 which positions the wiper174.

The aileron and rudder networks are connected together through a bridge80 consisting of an aileron trimming potentiometer 81 having a resistor82 and a wiper 83, a rudder trimming potentiometer 181 having a resistor182 and a wiper 183, and a fixed resistor 84. Wiper 83 of ailerontrimming potentiometer 81 is connected to wiper 33 of the rebalancingpotentiometer 31; wiper 183 of the rudder trimming potentiometer 181 isconnected to the wiper 133 of the balancing potentiometer 131; and theresistors 82 and 182 of potentiometers 81 and 181 are connected togetherso that they are in parallel. The parallel circuit thus formed isgrounded through fixed resistor 84, while the other side of the parallelcircuit is connected to a bridge 85 consisting of a potentiometer 86having a center tapped resistor 87 with wiper 88, and a souce of powersuch as a transformer 89 having a secondary winding 90 and a primarywinding 45. The resistor 87 is connected across the terminals of thesecondary 90 of transformer 89, the center tap of the resistor isgrounded, and the wiper 88 is connected to the bridge circuit 80 aspreviously mentioned. Since one of the input terminals of each of theamplifiers 13 and 14 is grounded, a completed circuit may readily betraced from the grounded center tap of potentiometer 86 through bridge80 to wiper 33 of rebalancing potentiometer 31, through the centeringpotentiometers 34 and 35, and through gyroscpopically operatedpotentiometer 40 to bridge 51, where it goes through the compensatingpotentiometer 58, picking up any signal from banking potentiometer 52,and then to bridge 70, going through center tapped resistance 71 andpotentiometer 72 and the Wiper 74 thereof to one terminal of theamplifier 13 and thence to ground. Similarly, a circuit may be tracedthrough the rudder network 11 and amplifier 14.

The elevator network 12 is generally similar to the aileron network andrudder network 11 and consists of three bridges 230, 251 and 270connected in series and to the elevator amplifier 15.

Bridge 230 includes a rebalancing potentiometer 231 having a resistor232 and a wiper 233, a pair of centering potentiometers 234 and 235having resistors 236 and 237 with wipers 238 and 239 respectively, agyroscopically operated potentiometer 240 having a resistor 241 and awiper 242, a source of power such as a transformer 243 having asecondary winding 244 and a primary winding 45, fixed resistors 246,247, 248, 249, and a three position switch 250. The gyroscopicallyoperated potentiometer 240 is connected across the terminals of asecondary 244 of the transformer 243, and a series circuit consisting ofthe centering potentiometer 234, the rebalancing potentiometer 231 andthe centering potentiometer 235 is likewise connected across theterminals so that this series circuit is in parallel with thepotentiometer 240. One end of the resistor 236 of the centeringpotentiometer 234 is connected to its associated wiper so that movementof the wiper will shunt a greater or lesser portion of the resistor 236.One end of resistor 237 of potentiometer 235 is likewise electricallyconnected to its wiper 239 and wipers 238 and 239 are mechanicallyconnected together so that as a greater portion of one resistor isshunted, a lesser portion of the other one is shunted and the totalresistance through the circuit consisting of potentiometer 234,rebalancing potentiometer 231 and centering potentiometer 235 remains aconstant as these wipers are moved. A resistance branch consisting ofthe fixed resistor 249 and fixed resistors 246, 247 or 248 is connectedin parallel with rebalancing potentiometer 231 and the resistance valuesof these fixed resistors is so chosen that they will form low, mediumand high resistance paths in parallel with the rebalancing potentiometer231. The resistance value desired may be selected by the three positionswitch 250, and I prefer to connect the three-position switches in eachof the three axes so that switches 50, and 250 may be simultaneouslyoperated from a single lever.

Wiper 233 of rebalancing potentiometer 231 is grounded, and wiper 242 ofthe gyroscopically operated potentiometer 240 is connected to bridge 251which includes an up-elevator potentiometer 252 having a center tappedresistor 253 and a wiper 254, a compensating potentiometer 258 having aresistor 259 and a Wiper 260, a fixed resistor 262 and a source of powersuch as a transformer 263 having a secondary winding 264 and a primarywinding 45. The up-elevator potentiometer 252 has the ends of itsresistor 253 connected together and through resistor 262 to one terminalof the secondary 264 of the transformer 263. The center tap of thepotentiometer 252 is connected to the other terminal of the secondary264 and also to one end of the resistor 259 of the compensatingpotentiometer 258. Wiper 254 of the up-elevator potentiometer 252 isconnected to the other end of resistor 259 of the compensatingpotentiometer 258, and since the ends of resistor 253 of the upelevatorpotentiometer 252 are connected together, it will be seen that therewill be no phase shift in the voltage appearing across the compensatingpotentiometer 258 as wiper 254 is moved from one side of the center tapto the other. Wiper 242 of the gyroscopically operated potentiometer 240is also connected to the center tap of potentiometer 252, and by varyingthe position of wiper 260 of the compensating potentiometer 258 anydesired percentage of the voltage appearing across the ends of thelatter potentiometer may be selected and carried on to the centeringbridge 270.

Centering bridge 270 is similar to the centering bridges 7t and of theaileron and rudder networks and includes a center tapped resistor 271, acentering potentiometer 272 having a resistor 273 and a wiper 274, and asource of power such as a transformer 275 having a secondary 276 and aprimary winding 45. The center tapped resistor 271 is connected acrossthe output terminals of the secondary 276 of the transformer 275 and theresistor 273 of the centering potentiometer 272 is likewise connectedacross these terminals so that resistor 273 and resistor 271 areconnected in parallel. Wiper 260 of the compensating potentiometer 258is connected to the center tap of resistor 271 and the wiper 274 of thecentering potentiometer 272 is connected to one of the input terminalsof the amplifier 15, which under certain conditions, is used to drivebalancing motor 277 which mechanically moves wiper 274 of the balancingpotentiometer 272.

One of the input terminals of amplifier 15 is grounded and it is thuspossible to trace a circuit from the grounded wiper 233 of rebalancingpotentiometer 231 through centering potentiometers 234 and 235, throughthe gyroscopically operated potentiometer 240 and the wiper 242 thereofto the bridge 251, where it continues through potentiometer 252 and itswiper 254 and compensating potentiometer 258, going from wiper 260thereof to center tapped resistance 271 and centering resistance 272,

from which it travels through wiper 274 to the amplifier 15 and then toground.

To'transfer control of' theamplifiers 13, 14, and 15 from the balancingmotors 77, 177, and 277 which position centering potentiometer wipers74, 174 and 274 respectively, to the .servomotors 16, 17 and 18operating the aileron, rudder, and elevator surfaces resp'ectivel-y,switching means 91, 191 and '291'ar'e provided in -the -'output circuitsof amplifiers 13, Hand 15.

It will be noted that I have'shown all transformers connected to thenetworks- 1:0, -1 1,=a'nd'12 as h'aving' a common primary 45. It will bereadily apparent that a single transformer having a plurality ofsecondary windings, or a number of individual transformers, or anycombination of "the two may be used. I

The details of the amplifiers -13, 14 and 15 and servomotors 16, 17 and1'8 fo1 rn no' part'of my invention, since such amplifiers andservomotors are well known in the art and may be any of a suitable type,such as that shown iinthe patent to Aris'ch utz-Kaempfe No. 1,586,233 or-Whitman No. 1,942,587. Likewise, I do not claim that part of networks10, 11,;and 12 consisting of bridges 30, 51, 130, 1:51, 230, and 251 inand of themselves, since sueh'networks are known and have not beendeveloped -by'rrle.

:In-the system shown herein, the Wipers 33, 133 and 233 of the balancingpotentiometers 31, 131 and 231 are operated by the 'servomotors 16, 17and 18 respectively. Th'e'wipers 38, and 39; 138 and 139; and 238 and239 of the centering potentiometers 34 and 35; 134 and 135 234' and 235respectively are manually operable; wipers 60, 1 60 and 260 ofcompensating potentiomete'rs 58, 158 and 258 are likewise manuallyoperable, wipers 74, 174 and 274 of balancing p'otentiometers 72, 172and 272 are operated by balancing motors 77, 177 and 277; wiper -88ofpotentiometer 86 is manually controlled and Wipers 83,"and 1-83 oftrimming potentiometers 81, and 181 may likewise be adjusted byhand.

A directional gyroscope 92, more fully described hereinafter, provides areference for any deviation of the plane in azimuth, and a mechanicallinkage 93 operates the wiper 54 of the banking potentiometer 52 andsimultane- 'ously operates the wiper 57 of the banking accelerationipotentiometer 55 whenever there is a deviation from a predeterminedheading. The linkage 93 also operates the wiper 142 of the ruddergyros'copically operated potentiometer 140 so that a total of threeWipers 54, 57, and :142 are simultaneously'oper'ated by the directionalgyroscope. A vertical gyroscope 94 is provided with mechanical means 95which measures any deviation of the plane about a roll axis, i. e.,about an axis extending lengthwise of the plane, and this mechanicalmeans 95 simultaneously operates the wiper 42 of the ailerongyroscopically operated potentiometer 40, the wiper 154 of the skidpotentiometer 152, and wiper 254 of the up-elevator potentiometer 252.Another mechanical means 96 is operated by the vertical gyroscope 94 toindicate any deviation of the plane in pitch axis, i. e., about an axisextending crosswise of a ship,and the means 96 operates the wiper 242'of the gyroscopically operated potentiometer 240 in the elevatorcircuit.

Operation of bridge circuits Neglecting for the present the method ofengaging the control system, if it is assumed that the airplane is nowunder'the control of the system shown herein with the switching means91, 191 and 291 connected so that the amplifier controls the operationof the servo motors 16, 17==and 18, it'will be seen that if there are nodisturbing influences and the plane is to remain in the same attitudeand on a'predetermined heading, there must be no movement of the controlsurfaces operated by the servo motors 16',- 17. and 18;; and theconstruction of the servo motors and theamplifiers '13,- 14 and whichare used in such that under these conditions 'tlrere must-he nosignalsrmm the aileron, rudder andeleva'to mo hs-10; fl and lz',respectively, 10 their respectiye: niplifiers. f l'ffthtough someexternal cause the zplane now' -deviates' "in-Iazhnpth, this "change inheadin will be sensed innnediately hy-the directional gyroscope 92fwhihwill-eause aheuinlr'age 93 to operate the-wipers 54 ands-7 ofthepetennsnierers 52 and :55:in the aneron network and also wiper-rel efthe gyrosco icallyoperated-potentiometer Mo in the rod-- der network.This leans -iliilfaf'gefsi-gnil t'oveloped across the endsorrheconrpeirs'atihgpe iit iome't'ei' 58, and the wiper fill thefeof w-illsend a portienof this signal to the bridge 7 ti thence t'o-theampIifierIS which in in n cperatest e aileron' se'rvo m6t0'r-16 seats tohank the plane to" u itsoriginal coursje, as win'be described inmore-dot ater; Sin'1iiItaheoi1s'ly,the wiper 142 of the gyroseo ie al-lyoperated' otentiometer: to-in the rudder network is moved from itsoriginal pos'ijtifon, and by the'p r inciple'o'f'the weuqmown'whenswseBridge, this will cause 'a "vol'tage signal to be deveIQpEd between thewiper 133 of the rehalanc'ing potentiometer"isl and the wiper 142,whihvt/"IH betransmitted through bridges 151 and to-the -'-amplifier=14'-whieh drives the servo motor-17 in a direetion to cause therhd'derto' turnthe ship toward its original heading.

Following new 'theyariousfisteps which occur as-the' dies the rudder-toa position to return gineil headingyrhc servoindto'r also o eratesthe'wiper 'lasoi therefinancingpotentiometer 131 so "that as the wiperis moved, the-signal developed 'acr'oss bridge'130 decreases *as therunner "reaches itsexneme 'posi 011. rlowever, thejmovernentof thcruudcrhas started-the turning "of the ship-toward its originalheading,and this correction has been "sensed by the utrcflctr nal gyroscope 92which thereuponstarts to returnnrcw iper 1420f the gyroscopicallyoperated potentiometer 140 to its original position. This -wi'11-eventually cause-the sign-a1 across the "bridgef'lfiti' to decrease to zerovalu'e'afidthen increase, but with a degreesphase shiftfroin'th'original signal. This phase shift is detected bytheafiipli'fii' 14 and the latter thereupon reverses the direction6ffotation of the servo motor 17 so that the rudder is graduallyreturned toward its neutral position.

A similar action has been taking place in the aileron network 10 savethat in that network the signal has been developed by the bridge 51, andtransmitted to the amplifier 13 which drives the servo motor 16, and thelatter operates the wiper 33 of the rebalancing potentiometer 31 so thata signal appears across the bridge 30 which tends to oppose thatappearing across the bridge 51. It will be remembered that thepotentiometers 52 and 55 in the bridge 51 cooperate to provide anexponential signal, i. e., a signal Whose voltage varies exponentiallyas a function of the displacement of the wipers from center and hence itwill be seen that for small deviations in azimuth only a small amount ofaileron correction is applied whereas for large deviations in azimuth adisproportionately greater amount of aileroncontrol is provided. It hasbeen found that a system which provides this exponential featureproduces the most accurate flying, since with small deviations, theplane is skidded intoproper position, while with larger deviations,coordinated recoveries are made.

The vertical gyroscope 94 may be of any suitable type of which there areseveral known in the art, and its action, as previously described, is tosense any change in the attitude of the ship about its roll or pitchaxes. As the plane tilts or banks about its roll axis, the verticalgyroscope 94 remains in its vertical position While the plane movesabout it, and wiper 42 of the gyroscopically'operated potentiometer 40,Wiper 154 of the skid potent-iometer 152, and wiper 254 of theup-elevator potentiometer 252 will thus be movedacross their respectiveotentiometers whichware rigidly mounted with res ect to the-transect theairplane. The' mcvemenr otwiper "4'2 9 with respectto resistor 41 of theaileron gyroscopically operated potentiometer -40 will unbalance the.bridge '30 and cause a signal to be sent to the amplifier 13 which willin .tu'rnoperate. the servo motor 16 to return theship to its original,position in much the same manner as has been. previously discussedexcept that no exponential signal. is introduced in the aileron network10. At the same time wiper 154 is moved with respect to resistance 153of the skidipotentiometer 152 to cause the signal to besent torthoaamplifier 14 to operate servo motor 17 and provide rudder action toassist in returning the ship to its previousIposi-tion. Theneed for bothaileronand rudder actionsto. restore. the .plane. to its original.position will be apparent when it is remembered that when one wing ofthe plane. is lower than the other, the plane tends \to turn toward thelower wing; and to overcome this tendency, ruddercontrol is needed tomaintainthe craft on its same heading While at the same time aileron-control .is applied tolbring :the wings back to their level position.Similan ly, taileron control is applied when the ship is making a turneas 'cont-rolled'from the directional gyroscope since the aileronsaaidconsiderablyin turning .a plane; in fact, in somelof thel-arger planesIhexshipmaybe turned by using ohlywthe aileronvand disregardingitherudder control.

f-Iolprovide means for adjusting therate of return from a lg'ivenangular deviation of the heading f the-plane, thercompensatingpotentiometer 58w'may be adjusted to select. thedesired :amountof bank,upon which the rate of return will depend. For :the most eflicientilying and for thegreatest :com'fortof the passengers, all turns andb'an-ksehouldtbe coordinated. That is, the resultant of the centrifugalforce in the turn and the acceleration due 'to..'gravity should heparallel Ito .the normal vertical axis 'of thepl'ane, and there willthus be no sensation of skidding which-zoccurs when the 'plane isinsufficiently banked rand objectslare urged outwardly from the centerof.the. turn) .DOI anyasensation of slipping (when the planetis too.steeplyabanked and objects are urged'ttoward' plane -whenever the:plane is banked, ascertain amount of .lift -is lost and i the ':plane.thus tends to 1 settle cor 'lose altitude even though it may retain thesame :attitudesas measured about its pitch axis. When a plane isoperated manually, the pilot applies up-elevator whenever he is in abank eithertto the right orleftxtoovercome this tendency; and 4 the tsame effect is obtained .in' this control system by themechanical means195imoving the wiper 25.4 --of t the up-elevator potentiometer. 252 awayfrom its center position whenever the; plane .:is sbanked 'to eitherside. i

As has beenpreviously mentioned, the .:movement of the"wiper 254towardeither side .ofsthe'potentiometer 252 -introduces a' signal. intothe network. 12:1vhich varies as the distance of the wiper: from center,but which has the samet-phasi ng on i either. side of: the centeritap'of the potentiometer. The signal? resulting from this movement of thewiper 254 of the .up-elevator potentiometer 252 is-i-phased so as tocause the amplifier 15 to operate the servo motor to drive the elevatorin an upward 'directio'n,'and by adjusting thewiperi260 of thecompensating-potentiometer "258 a sufiicient amount of the up.-elevatormay be obtained to maintain the craft at the same altitude whileit remains in the bank.

"Thevertical gyroscope94.also-operates tomaintain the. craft in its sameattitude about its pitch .axis so'lthat it does not nose up orddown andthusclimb i -"dive. This is done. by the'mechanical. means 96 whichdetects any variation about-thepitch axis of theplane and moves thewiper .242 of the tgyroscopically operatedapo-v tenti'ometer 240 so thatthe bridge 230 then develops=a signal which is transmitted totheamplifier :15 to control the elevator servo motor 18 andapply thenecessary corrective movement ztothe elevator itself. The operation ofthe servo motor 18 .drivestthe wiper 233 of the rebalancingpotentiometer 231 and the sequence of operation is then similar to thatdescribed in the operation of the rudder network previouslycovered. Itshould be noted .that -.the up-elevator potentiometer .252 is connected.so Ethatany movement of its wiper 254 from its center position willcause the .servo motor 18-to drive the elevator .upwardly whereasmovement ofthewiper 242 of the gyroscopically operated potentiometera240will cause the elevator :to be. driven upwardly when moved to one sideof center a and downwardly whenmoved to the other side of center.

When the .plane is flying under the control of this system .andritisnoted that because of shiftingload, different amounts of power intheengine of either wing, or for any other reason the plane is not inthe desired attitude,

the centering otentiometers 34 and 35; 134 and 234 and 23.5 may .beused. to change the position of the ailerons, rudder, or elevatorrespectively. To understand .the operation 30f :this, let it be assumedthat the bridge .30. of theaileronnetwork 10 isbalanced so thatitdevelops no voltage between the wiper 33 of therebalancing;.potentiometer 31 and the wiper 42 of the gyroscopicallyoperated potentiometer 40, and-that wipers 33 and 42 are inthemid-,positionsas are wipers 38 and 39 of'the centering -.potentiometers34 and35. If the wipers 38 and 39 of the centering .potentiometers 34and 35 are now. moved ,to the ,position shown in Figure 1, resistancewill have been added tothe lefthand side of the bridge and movedfromttheright. hand side of the bridgecreating anunbalance.andcausing.thearnplifier 13 to drive the servo motor .16 soasto-move the .wiper 33 of the balancing potentiometer 31 toward .theleft, until anew balance point is reached. The ailerons, of course, havebeen movedby the operationoftheservo motor ;16 and the. airplane hencemoves about its roll. axis. until. a; new point of balance for the.controlsystemis established.

As is well'knownto those familiarwiththeopenation of airplanes, at lowair speeds it is. necessary .tmsecurela much greater movement ofthecontrol surfaces -.to produceja given rn aneuver that it. is at highairspeedspand: sinee'to ,haveacontrol system which will be satisfactory, itmust operate the air plane properly: at low, medium and high "speeds,pr,ovision has been made for varying-the amountof control surfacedisplacement. fonagivenqdeviation of*the plane from its predetermined,position. .As shown' in theaileron. network 10, Ihave; providedathreepositionswitch 50 which permits any one of the three fixedresistors '46, "47 or 4.8 to be connectedin. serieswith fixed resistor*49'and in parallel with.the balancingtpotenfiometerfil. Applyingthelaws of elementary electricity,

the resistance across-the parallel circuit thus formed will.

be thellowest when the low resistance'fixed resistor isin the circuitand highest when the highest resistance finefd resistor is inthecircuit; andsincethe combined resistance of the centering; otentiometers.34 and35 remain aconstant, the total resistance across the. seriesparallel circuit including the centering;potentiometersi34 and 35,.reba1 ancing "potentiometer31, 'an'd fixed. resistors 4.6, 47,. 48 and49 will vary as 'switch=50 is thrown to its diflierent positions. Sincethe' voltagesupplied. by the secondary 44. of the transformer 43remainssubstantiallya constant, and since the voltage drop across-the--individual resistors in .a series circuit varies as theirresistance, it follows that when a low resistance fixed resistor isconnected in series 'with the fiXfid'i-TESlStOl' t49,.-thepotentialdifference acrossthe ends of the resistance )32'of therebalancingpotentiometer 31 will be lower; and when: a high resistancefixed-resistor is .connected ina series with the fixed IGSlStOIl49, thevoltage drop across .the resistor 32willbehigher.

It is apparent that the control system described herein operates on asystem of balanced voltages, and if a given signal is put into theamplifier, the servomotor will be driven until a corresponding voltageof opposite phase is introduced by the rebalancing potentiometer 31. Ifthe voltage drop across the potentiometer 31 is small, corresponding toa condition when the switch 50 is connected to a low resistance fixedresistor, the wiper 33 must be moved a greater distance to equal thegiven voltage signal than when the voltage drop across the potentiometeris high. Thus, when a large movement of the aileron control surfaces isdesired, corresponding to a low airspeed, the switch 50 is connected toa fixed resistor having a low resistance value, and when small movementof the control surfaces is desired, corresponding to a higher airspeed,the switch 50 is connected to a resistor having a high resistance. Asimilar method of providing means for adjusting the degree of controlsurface movement is provided in the elevator bridge 230 and a comparablemethod based on the same general theory is provided in the rudder bridge130.

If it is now assumed that the plane is flying under the control of thissystem, maintaining the proper heading, altitude and attitude andcorrecting for any deviation therefrom, the pilot may still desire toturn the ship to a new heading; and to do this he could use thecentering potentiometers 34 and 35 in the aileron circuit to provide theproper amount of bank and then use the centering potentiometers 134 and135 to secure the proper amount of rudder control to provide acoordinated turn. However, this is not a very satisfactory method ofmaking turns and hence the turn control bridge 85 is provided. To make aturn the pilot merely moves the wiper 88 of the potentiometer 86 to oneside or the other, depending upon the desired direction of turn, and avoltage will be developed between the wiper 88 and the grounded centertap connection of the resistance 87. This voltage is then applied to oneside of the bridge 80 which has the other side grounded through a fixedresistor 84, and by adjusting the position of the wiper 83 of thetrimmer potentiometer 81 the turn control bridge may be calibrated toprovide the desired bank for a given amount of movement of the wiper 88.Similarly, the amount of rudder control necessary to provide acoordinated turn for this amount of bank may be secured by adjusting thewiper 183 of the trimmer potentiometer 181; and hence by turning asingle turn control potentiometer 86, the proper signal in the properamount may be introduced in both the aileron and rudder networks toprovide a coordinated turn.

It will be seen that if no other means were provided, as soon as theturn was made with the turn control potentiometer 86 the ship wouldchange its heading and the directional gyroscope would sense this andprovide a correcting signal to bring the ship back to course. To takecare of this condition, locking means, to be described later, lock themechanical linkage 93 against movement'whenever a turn is made by meansof the turn control potentiometer 86, and hence all of the wipersoperated by this linkage are held in center position and no signal isput in tending to return the ship to its original heading.

Considering now a portion of the procedure which must be followed beforeplacing the system in operation by connecting the amplifiers 13, 14 andto the servo motors 16, 17 and 18, it will be apparent that the wiper 88of the turn control potentiometer 86 should first be centered so that nosignal will be fed into the aileron and rudder networks 10 and 11 fromthe turn control bridge 85. The wipers 38 and 39; 138 and 139; and 238and 239 of the centering potentiometers 34, 134, 135; 234 and 235respectively are also preferably in center position so that it will bepossible to trim the ship by moving all of the control surfaces ineither of their directions. The wiper 54 of the banking potentiometer52, the wiper 57 of the banking acceleration potentiometer 55, and thewiper 142 of the rudder gyroscopically operated potentiometer shouldalso be centered so that the directional gyroscope 92 will have equalcontrol in either direction in azimuth. The airplane itself should betrimmed so that it is flying in the proper attitude and on the properheading; and since the control surfaces will then be adjusted so as tomaintain the plane in its proper attitude and heading, it is importantthat under all these conditions that the signal from the networks 10, 11and 12 to the amplifiers 13, 14 and 15 respectively be zero so that whenthe corresponding servo motors 16, 17 and 13 are connected to theirrespective amplifiers there will be no movement of any control surfacewhich would tend to cause the plane to change its attitude or heading.Because of loading or other conditions, it may be necessary to use acertain amount of aileron control surface in order to hold the wings ofthe ship level; and in such a case a signal would be developed in thebridge 30 and transmitted on to the amplifier 13. This signal must becanceled by an opposing signal so that the aileron servo motor 16 willnot be driven when it is connected to the amplifier 13; and to providethis opposing signal, switching means 91 is arranged so that when theamplifier is not connected to the aileron servo motor 16, it isconnected to the aileron network balancing motor 77, this being atwo-position switching means with no off position. The balancing motor77 is a small reversible motor whose only function is to drive the wiper74 across the resistor 73 of the potentiometer 72, and thecharacteristics of this motor are such that if there is a signal throughthe amplifier which would operate the servo motor 16, that same signalwhen going to the balancing motor will drive the latter so that thewiper 74 is moved in a direction to oppose and counteract the signalfrom the remainder of the network 10. As soon as me signal from theremainder of the network 10 is counteracted, the signal through theamplifier becomes zero and there is thus no signal to the balancingmotor from the amplifier and movement of the wiper 74 is stopped. Theswitching means 91 may then be operated to connect the amplifier 13 tothe servo motor 16 and there will be no movement of the servo motorwhich would drive the control surface and cause the ship to lurch. Theoperation of the balancing motors 177 and 277 with regard to the signaldeveloped by the networks 11 and 12 respectively is the same, and itwill thus be seen that it will be possible to operate the switchingmeans 91, 191 and 291 to engage the control system on all the axeswithout there being any lurching of the plane or any violent movement ofany of the control surfaces thereof.

Power circuit In Figure 2. I have shown a power circuit for use with mycontrol system, making use of several safety features not previouslyavailable. a source of power such as the ships batteries 301 orgenerators (not shown) or both is connected to the usual single wirepower system used in planes, with one terminal of the battery groundedand the other terminal connected through the planes master switch 302 toa bus bar 303. Connected to the ships bus 303 is a system master switch304 which energizes a system bus 339, and all power to the controlsystem is controlled by this switch so that in case of emergency it isnecessary only to open this switch and all operation of the controlsystem immediately ceases. When the switch 304 is closed, power flowsfrom it through the coil 305 of a current sensitive relay 306 and thenthrough conductor 309 to the directional gyroscope 92 where it energizesthe motor 307, shown in Figure 3, driving the rotor of the gyroscope.The characteristics of the motor 307 are such that when it is initiallyenergized and during the major portion of the time it is accelerating,the amount of current it draws is considerably above the amount drawnwhen it has reached its final operating speed. The current sensitiverelay 306 has a pair of contacts 308 which are normally In the powersystem shown,

13 in a closed position, butj which are opened when the current throughthe coil 305 exceeds a predetermined value. The current sensitive relay306 is adjusted so that upon starting the motor 307 hand-continuinguntil it has reached a speed sufli cient to give the gyroscope anappreciable spatial rigidity, the contacts 308 remain open; but when thegyroscope-has acquired the necessaryrigidity the contacts are closed anda circuit is completed through them from the master switch 30 i throughconductor 310, to a torque motor 323 whose function -and operation arehereinafter described.

'To provide the alternating current'necessary to operate the Controlnetworks previously described, an inverter 311 is prov-ided which hasits input circuit connected to the master switch .304 andto ground, andhas its alternating current output circuit connected to the varioustransformers of the control network :and may also be connected as shownto the amplifiers 13, 14 and 15 for use as a power source therein shouldthat appear desirable. =If direct current power is also desired in theamplifiers they may likewise be connected to the switch 304 and beenergized therefrom. n H

The closing ,of switch 304 also energizes the vertical gyroscope 94which has connected in series withitspower an operating coil 312 of acurrent sensitive relay 313*, thecontacts 314fo f which are normally,opened but are adapted to be closed when the gyroscope is firstenergized and toremain closed until it has reached a speed sufiicient toprovide thenecessary'spatial rigidity.

, Whent-he switch 3M is closedit willthus be seen that the directionalgyroscope "92 is energized and the motor therein starts to rotate andbring the gyroscope up to speedpand as, it approaches its normaloperating speed contacts 3080f rela /.306 are closed and thetorque motoris energized. At the same time that the directional gyroscope 92isenergized, the inverter'311is energized, and startsto deliveralternating current to the networks 10, 11 and 12 which aretherebyplaced in operative conditi'o'n, the amplifiers 13, 14 and 15areenergized by the inverter 'and/or th'e power flowing directly fromswitch 304, and'the'vertical gyroscope 9'4 is likewise energized sothanthe rotor therein begins to revolve and is erected to averticalpositionby means not shown. It will be apparent that during thiswarm-up period, while the gyroscopes "are erecting and attaining theirspatial rigidity, the servo motors 16, 17and 1d should not :be connectedto their respective amplifiers 13, 1'4 and 15, since thetransientconditions present during this period would cause erratic movement ofthe control surfaces with resulting undesired movement ofthe plane.During this period, thereforethejoutput of the amplifiers 13, '14- and15 is directed by the switching means 91, 191 and T31 to the respectivebalancing motors 77, 177 and 277 so that the networks 10, 11 and12 arec-ontinuallybalanced as these transient conditions may require. Whenthese transientconditions have passed and it is desired to have thissystemcontrol the flight of the plane, a switch 315 may be thrown tocomplete a circuit from the masterswitch 304 through switch 315,conductor 320, the con-- tacts 316 of a relay317, and conductor 321 tothe oper-- ating coil 318 of a'relay 319. The energization of the coil318 of the relay319 acts to operate the switching rneans91, 191*and291sothat the output of the amplifiers '13, 14 and 15 is transferred from thecorresponding balancing motors 77, 177 and 277 to the correspondingservo motors 16, .17 and 18. Under these conditions the networks 10, 1 1and 12 have been balanced so that no signal is sent from them to theamplifiers which would cause the servo motors to drive the controlsurfaces to new positions when the control system is engaged.

If, in spite of its balancing motor, for some reason or other one of thenetworks is unbalanced and it transmitting a signal to its amplifiers, asignal will be sent to the corresponding centering motor and that samesignal. would be sent to the servo motor should the relay 319'beoperated to transfer thewamplifier output to ther-servo motor. Thiswould cause theplane "to lurch-and is generally undesirable.

To prevent the engaging 'of the system until each rhetwork is balanced,therrela-y 517 is provided with anumw ber of coils 'each one of which iscapable of attracting thei -armature of the relay and thus "opening the,circuit between the'contacts 1316. Oneof the coils of the relay 317 isconnected through conductor "358, :contacts 314 of the current sensitiverelay 313, and conductor1359 to the master switch304so thatshouldthevertical gyroscope be rotating at 'afspeed below that needed to vg'iveitsufficient rigidity, the contacts 314 willbe closedand the associatedcoil in the relay 317 will be energized. and thereby open the contacts316 to prevent the operations of the relay 319. I have connected theremaining coils of the relay 317 so that each one is in parallel with'acorresponding "Winding otf one of the balancing motors, so that shouldany oneof the. balancing motors be receiving a signal tending to drive"it in-e'ither direction when an attempt is made toengagethe-rcontrolsystem, at least one of the windings of the relay 317 will be energizedand "the contacts 316 will be open and so prevent the operation of relay319 to'transfer'the output of the amplt iier to their'respective servomotors. In case-the plane is flying in rough'air, minor-changes in itsaltitude will beoccurringcontinuously; and if no provision were made forthis, these changes in attitude would cause the relay 317 tobe energizedalmost contiriuously becans'eofthe slight changes of position requiredof the balancing motors. To take care of this contingency, I provide atime delay means "on the relay 317 which may take the form of a timedelay slug 32-2 which will-prevent the operation ofthe relay :untiloneor more of the coils has been continuously energized for -anappreciable time: Multiplecoil relays and time delay slugs are well:known in the art, and-any suitable-u-nitsmay-be used.

it will thus be seen that"-I"have provided "a system in which theclosing of one -switchenergized the control networks and starts therotating wunits, but engagement oi the system i prevented until therotating units are up to speed and the control networks arebalanced.-I'n this connectionit' mi-ght be well i'OfIlOiG'ilhdi. in'lairplaneelectrical systems the voltage availableatthe main bus 303 often varies'over awide range,-and under these conditions it may be d'ilficult ifnot impossible to :adj-ust the current sensitive relay 313 -in serieswith the vertical gyroscope 94 so that the contacts 314 will benopenedimmediately upon the gyroscopes being; 'erected andrcoming up't-ospeed-and not before .then. If voltage fluctuations cause thesetroubles, it is possible, of course, -to substitute a time -delayrelay=of any suitable \type,-adj ustable to the proper time interval,"for the current sensitive relay 313. .A portion of the-circuit shown inFigure "2 is shown with a time :delayswitchsin place of thecurrentsensitive relay, in Figure 2a In this figure- I "have. shown atime delaylswitch 391 which may be of anysuitabletype; such as thermal,motor driven, etc., and whichis energized when the vertical gyroscope 94isenergized, tocomplete a circuit through conductors 358 and 359 to awinding of multiple-ooilrelay 317. After apredetermined period of time,sufiic'ient for the rotor of the gymscope94+to come up to speed, thecircuit-is opened, and the remainder of the operation is the same asthat previously described. Timing relays generally work very well, butmotor driven time delays are usually not so satisfactory since fromtheir nature, if "the systems master switch 304 is opened and thenimmediately closed, the pilot must wait the full.

period of thetime delay beforehecan reengage the control system,although it will be apparent that the momentary interruption ofcurrentto the vertical gyroscope will not have caused it to losesufiicient speed to require erecting again; or to havelost'its.spati'al'rig-idity.

Turning now to the directional gyroscope r and 'theolementswassociatedwith it which areinow'of interestjsome of these elements are a torquemotor 323, a directional arm lock or DAL. 324, and a directional panel325. As may be seen in Figure 4, the directional gyroscope 92 includesan enclosed rotor 326 having the motor 307 therein (not shown) pivotallymounted for rotation about a horizontal axis and supported by a cardanring 327 which is rotatable about a vertical axis passing through itscenter. A cardan gear 328, concentric with the vertical axis of rotationof the cardan 327, is mechanically connected to the latter so that thetwo rotate as a unit; and slip rings 329 axially spaced from the gear323 and concentric therewith provide means for supplying power to themotor 307 within the housing 326. Above the slip rings 323 and rigidlyconnected to the card-an gear 328 and concentric therewith is a clutchdrum 330 which may be engaged by a ring 331 to which is attached adirectional arm 332. The ring 331 is split and provided with expandingmeans (not shown) which permit the clutch drum 330 and the ring 331 tocooperate to form a clutch which may be engaged or disengaged to permitmovement of the directional arm 332 as the cardan ring 327 turns aboutits vertical axis. Stops, not shown, are provided which limit themovement of the directional arm 332, and when the arm has reached one ofthe limiting stops, further movement of the cardan ring 327 causes theclutch drum 330 to slip within the ring 331.

As is Well known to those familiar with gyroscopes, when an externalforce is applied to a gyroscope tending to turn it about an axisperpendicular to its axis of rotation, the gyroscope actually turns orprocesses about an axis perpendicular to the axis of rotation of thegyroscope and perpendicular to the axis about which the force is acting.As is also known to those familiar with gyroscopes, a gyroscope tends toretain its heading in space unless caused by external forces to changethis heading. While the rotor of the gyroscope 326 does exhibit thesecharacteristics of spatial rigidity, the friction of the cardan gear328, slip rings 329, directional arm 332, and associated equipment issufficient to cause the cardan ring 327 and hence the gyroscope 326 tobe rotated about a vertical axis when the ship is turned in space.However the rotation of the cardan ring about its vertical axis appliesa torque or turning force to the gyroscope 326 and causes the latter tomove about a horizontal axis perpendicular to its axis of rotation sothat the gyroscope bobs or tilts.

This bobbing or tilting of the gyroscope may be used to control meansfor overcoming the eifect of the frictional drag on the gyroscope. andthis may be done by providing a wiper 333 which may make contact withany one of a series of sectors 334, 335, 336 and 337 mounted on aninsulating plate 338 which is attached to the cardan ring 327. Thesectors 334 and 335 are so located that they will be contacted by thewiper 333 when that end of gyroscope has tilted below the horizontal andcontacts 336, and 337 are so located that they will be contacted by thewiper 333 when that end of the gyroscope has tilted above thehorizontal, thus leaving a space between sectors 335 and 336 on whichthe wiper 333 will ride when the gyroscope is horizontal.

To provide the restoring force necessary to keep the rotor 326 of thegyroscope horizontal, the torque motor 323 is provided, consisting of acontinuously running motor 340 driving a pair of gears 341 and 342 sothat they rotate in opposite direction. As shown in Figure 4, the lowersurfaces of gears 34]. and 342 are provided with clutch plates 343 and344 respectively, and axially movable into engagement with these clutchplates are the associated clutch plates 345 and 346 respectively.Connected to the movable clutch plates 345 and 346 are pinion gears 347and 348, respectively, both of which are continuously meshed with gear349 which drives gear 350, the latter gear being meshedwith the cardangear 328. Normally, the clutch discs 345 and 346 do not engage theirassociated discs 343 and 344, but when, as shown in Figure 4, disc 346engages its associated disc 344, the gear 342 attempts to rotate thegear 348 and this attempted rotation is transmitted through gears 349and 350 to the cardan gear 328, thereby attempting to rotate thegyroscope rotor 326 about its vertical axis and hence causing it to tiltabout its horizontal axis. To move the clutch discs 345 and 346 intoengagement with their associated discs 343 and 344 respectively, a pairof electromagnets 351 and 352 which have armatures 353 and 354 areprovided. The armatures 353 and 354 are adapted to bear against the endsof their respective gears 347 and 348 and urge the associated movableclutch discs 345 and 346, respectively, into engagement with clutchdiscs 343 and 344 when their associated electrom-agnets 351 and 352 areenergized.

The electromagnets 351 and 352 are selectively energized by means of theWiper 333 and contacts 334, 335, 336 and 337; and as shown in Figure 4,electromagnet 352 is energized by reason of the fact that wiper 333 ismaking contact with sector 334 and hence gear 342 is attempting to drivethe cardan gear 328 which will result in the rotor 326 of the gyroscopebeing returned to horizontal position. Sectors 334 and 337 are connectedto separate slip rings 329 and sector 335 is connected through aresistor 356, shown in Figure 3, to the same slip ring that sector 334is connected, while sector 336 is connected through a resistor 357 tothe same slip ring that sector 337 is connected. The eifect of resistors356 and 357 is to provide a smaller impulse to the electromagnets 351and 352 when the inner sectors 335 and 336 are connected by the wiper333 than when the outer sectors 334 and 337 are similarly contacted.This means that a smaller amount of torque will be applied to the cardangear 323 when the gyroscope rotor 326 has tipped a small amount thanwhen it has tilted through a larger angle. Stops 360 and 361 areprovided in the cardan ring 327 to prevent the gyroscope rotor 326 fromtilting too far before the torque motor 323 can return the rotor to itshorizontal position.

The directional gyroscope which I have just described in and of itselfforms no part of my invention since such gyroscopes are well known inthe art, and the description has merely been included in order to pointout more clearly the features and the operation of the improvements Ihave developed therefor.

The operation of the directional arm lock 324 may now be more clearlyunderstood, reference being had to Figures 2, 3 and 4 of the drawing. Ashas previously been mentioned, for proper operation of the controlsystem it is necessary that the wipers 54 and 57 of the bankingpotentiometer 52 and the banking accelerating potentiometer 55 and thewiper 142 of the rudder gyroscopically operated potentiometer 1.49 mustbe centered with respect to the ends of the resistors of theirrespective otentiometers before the control system is engaged, and whenturns are being made with the control potentiometer 86 while the systemis engaged. Since the operation of the directional gyroscope 92 and itsassociated po-tentiometers is to keep the plane headed so that thewipers of these potentiometers remain in substantially their centerposition during normal fli ht, all that remains to be done is to insurethat the wipers will remain in this position when a turn is made by thecontrol potentiometer 86. As previously described, the wiper 88 of thecontrol potentiometer 86 is manually operated, and mounted on the sameshaft as the wiper 88 is a cam member 363 which operates a switch 364 sothat the contacts of the latter are opened when the wiper 88 is in itsmid position and closed when it is moved to either side thereof. Thedirectional arm lock 324 consists of a solenoid 365 which, whenenergized, attracts a clamping bar 366 which then moves to bear againstarm 367 which, like arm 332, forms a portion of the mechanical linkage93 connecting the directional gyroscope 92 to its various potentiometerwipers. The arm 367, which is normally movable back and forth asindicated by the arrows in Figure 3, will then be clamped so that it canno longer move, and slippage will then occur between the clutch 1 7 drum330 and the ring 331. To energize the solenoid 365, a circuit iscompleted from system bus 339, through switch 364, conductor 362,solenoid 365, and through a wiper 371 and contact 374, described later,to ground. When the contacts of switch 364 are opened the solenoid 365is deenergized and the arm 367 is released.

To provide means for centering the wipers of the various directionalgyro controlled potentiometers before the control system is engaged, Ihave made use of the motor 340 of the torque motor 323, and theelectromagnets 351 and 352 associated therewith. This centering isaccomplished only when the system is not engaged and is controlled by apair of wipers 370 and 371 connected to a gyroscopically operated armwhich may be an extension of directional gyro arm 332, the wiperscooperating with a series of contacts 372, 373 and 374. The wiper 370may bear against contact 372 and 373 or neither of them, this lattercondition occurring when the wipers of the potentiometers operated bythe directional gyroscope are centered; and wiper 371 bears againstcontact 374 when the wipers of the potentiometers are centered. Thecontacts 3'72, 373 and 374 together with the wipers 370 and 371 may beconveniently located within the panel which houses the potentiometersoperated by the directional gyroscope,

this housing being referred to as the directional panel 325.

Contact 374 is grounded, and when wiper 371 makes contact therewith acircuit is completed to the coil 365 of the directional 'arm lock 324. Acircuit may be traced (Figure 3) from ground to the contact 374, throughthe wiper 371, through the solenoid coil 365, and, when the controlsystem is engaged, through switch 364 and switch 304 to the energizedside of the planes electrical system as indicated by the bus 303. Whenswitch 315 is in the autopilot disengage position shown in Figure 2, i.e., so that it energizes conductor 362, it shorts switch 364 to energizecoil 365 of directional arm lock 324 from whence the circuit iscompleted through the wiper 371 and contact 374 as previously mentioned.

In addition to energizing the solenoid 365 of the directional arm lock324, the wiper 371 and contact 374 cooperate to energize the winding 380of a relay 381, the other end of whose winding is connected, with theungrounded side of the torque motor 340, through the contacts 308 of thecurrent sensitive relay 306 to the master switch 304. This relay has twopairs of normally open contacts 382 which interrupt the circuit from theslip rings 329 to the electromagnets 351 and 352 of the torque motor323, the result being that in order for the wiper 333 on the end of thegyroscope rotor 336 to have any effect upon the horizontal position ofthat rotor when contact is made with one of the sectors 334, 335, 336 or337, the wiper 371 must bear against contact 374 and energize the relay381 to complete the circuit to the electromagnets 351 and 352.

When wiper 371 is not touching contact 374, wiper 370, which moves withwiper 371, will then be touching either contact 372 or 373; and theselatter contacts are connected to selectively energize the electromagnets351 and 352 of the torque motor 323. The operation under theseconditions can be best understood by referring to Figures 4 and 5wherein it is seen that wiper 37 0 is hearing against contact 372 andwiper 371 is not touching contact 374. The contacts 382 of relay 381 arethus open and, as seen in Figure 4, electromagnet 352 is energized sothat gear 342 attempts to drive the cardan gear 328. As previouslyexplained, this will cause the rotor 326 of the gyroscope to tilt, butsince sectors 334, 335, 336 and 337 are disconnected from theirrespective electromagnets 351 and 352, the tilting will cause nocorresponding action of the electromagnets, and the rotor 326 willcontinue to tilt until it hits one of the stops 360 or 361. As is normalunder such conditions, when a torque is applied to a gyroscope and thelatter tilts until it hits a stop, further application of that torquewill cause rotation of the gyroscope in the direction of the appliedtorque, which may then be of greatly reduced value. Consequently, whenwiper 370 bears against contact 372, electromagnet 352 is energized,clutch plate 346 moves into engagement with clutch plate 344 and gear342 drives the cardan gear 328 causing the gyroscope rotor 326 to turnand the whole assembly of gyroscope, cardan ring 327, cardan gear 328and associated equipment to rotate, thereby moving wiper 37 0 towardscenter. When wiper 370 reaches its mid position, its connection withcontact 372 is broken, releasing the electromagnet 352 and stopping thedrive of the cardan gear 328; at the same time wiper 371 has madeconnection with contact 374, energizing the locking solenoid 365 andalso energizing the relay 381 which thereupon restores the normalcircuit of the wiper 333 and contacts 334, 335, 336 and 337 so that thegyroscope rotor 326 is then returned to its horizontal position. Sincelocking solenoid 365 is energized as soon as the wipers 370 and 371return to their mid position, the directional arm 367 is immediatelylocked in position and there is thus no possibility of angular momentumcarrying the cardan gear 328 past its desired position and hence drivingwiper 370 beyond its mid point so that it bears against contact 373.

To prevent wiper 370 and contacts 372 and 373 from completing a circuitwhich would cause the torque motor 323 to revolve the rotor 326 andcenter the various potentiometers controlled by it when the plane isbeing controlled by the automatic pilot, I provide a relay 385 having anoperating coil 386, a normally open contact 387, a normally closedcontact 388, and a movable contact 389 adapted to bear against either ofthe other two contacts. Movable contact 389 is grounded, and normallyclosed contact 388 is connected to wiper 370, so that when coil 386 isnot energized, wiper 370 is grounded and the operation is as previouslydescribed. Normally open contact 387 is connected to wiper 371, and thuswhen coil 386 is energized, wiper 371 is grounded through normally opencontact 387 and movable contact 389 irrespective of whether wiper 371 isbearing against contact 374 or not. Thus, when operating coil 386 isenergized, movable contact 389 opens the ground circuit to normallyclosed contact 388 and grounds normally open contact 387, therebypreventing wiper 370 from completing a circuit to electromagnets 351 or352, and also continuously grounding wiper 371 so that relay 381 iscontinuously energized to close contacts 382 and maintain the normalcircuits to the electromagnets 351 and 352 from slip rings 329. Toenergize operating coil 386, one end thereof is grounded and the otherend is connected by conductor 390 to conductor 320, and hence relay 385is operated when switch 315 is in the position wherein switching relay319 may be energized. In this way, the potentiometer wipers controlledby the directional gyroscope 92 will automatically be centered when theswitch 315 is in the position shown in Figure 2, but when the switch isthrown to its other position and the autopilot is engaged, the centeringcircuits are broken and any deviation of the plane from its assignedheading will cause a movement of the wipers controlled by thedirectional gyroscope 92, and they will be returned to their centeredposition only 'by return of the plane to its original heading.

Operation of the power system It may now be appreciated that myinvention has simplified the operation of a control system such as this,since the operations which a pilot must perform in order to engage thissystem have been enormously simplified and reduced over those necessaryin previous systems.

To prepare the system, assuming that the plane is airborne and that themaster switch 302 is closed, the pilot must first close control systemmaster switch 304 and then trim the plane manually so that it has the desired attitude and heading. When the system is so prepared, power isimmediately applied to the directional stabilizer 92, the inverter 311,the amplifiers 13, 14 and 15, the vertical gyroscope 94. The bridgenetworks 10, 11 and 12 are thus energized and the amplifiers 13, 14

19 and are energized and warming up; the'torque motor 323, because ofthe large initial current through the current sensitive relay 366, isnot energized; and the similar large current drain by the verticalgyroscope 94 through the current sensitive relay 313 has closed thecontacts 314 thereof and energized the corresponding coil of the relay317 so that the contacts 316 thereof are open. The relay 319 is thus notenergized, and the switching means 91, 191 and 291 are thus transmittingthe power output of the amplifiers 13, 14-and 15 to the correspondingbalancing motors 77, 177 and 277 so that as the amplifiers warm up,anysignals developed in the networks 10, 11 or 1 2, will be used todrive the balancing motors so that these 'signals'are balanced out. Asthe directional gyroscope 22 gathers speed, the current it-draws will-be reduced and eventually the contact 398 of the current sensitiverelay 306 will be closexland the torque motor 323 energized. Were it notfor this delay, and if the torque motor were energized at the same timethat the directional-gyroscope were energized, the gyroscope would haveno spatial rigidity and the torque applied to it by the torquemotorwould rotate it v'eryrapidly and thereby cause the rotor326 to bangviolentlyagainst its stop and probably dam-age the bearings-of'therotor.

When the torque motor-323 is energized, the automatic centering meansconsisting of the wipers 370, 371 and their associated contacts causethe mechanical linkage 93 to'be-driven softhat-the wipers 54 and 57 ofthe banking potentiometer'52 and'the'banking accelerating potentiometer55 respectively,and thewi'per 142 of the rudder gyroscopically operatedpotentiometer '140 are placed in their centerpositions. In addition, thedirectional arm lock 324 is energized 'as soon as these positions areattained and hence there will be no further movement of these -wipersuntil'the sy'stem is engaged.

When the plane hasbeen trimmed to the satisfaction of the pilot, thedirectional gyroscope 92has attained a suflicient speed to -allow'thecontacts 308 to close and energize the torque motor 323, the'verticalgyroscope 94 has attained a sufiicient speed 'to enable the contacts 314of the relay-313-to*open,-and*tl1e balancing motors 77, 177 and 277 havebalanced out all but momentary and transient signals from --the aileron,"rudder, and elevator networks '10, -11-and-1 2,'the contacts 316 of therelay 317 will then-be closed a'nd the pilot may throw switch 315-tocomplete a--circuit through contacts 316 and coil 318 ofrel'ay-319"andthen to ground, thereby operating the switching means '91, 191' and 29lto transfer the power-output'of-the"amplifiers 13, 14 and 15 to theservo motors 16, "1'7 and '18. Thus, all that the pilot has to do'is tothrow the master'switeh 304, arid then, after a period sufiicienttoenable "the gyroscopes to assumetheir proper speed,'thr'ow switch 315and the control system is then'engaged and flying the 'plane. Changes inattitude and changes in heading may be takencare ofaspreviouslydesribed,'andit will thus be seen that I have providedacontrol system which operates to provide an-extremely sensitive controlof great flexibility while, at the same time providing this system withan operating procedure so simple that a pilot who has had no experiencein its use may become very proficient with only a few minutesinstructions.

Because of the superiorityof electrically operated automatic pilots, Ihave shownand described my invention as it may be applied to one ofthese. It is particularly adapted to such asystem, though it may be seenthat with slight'modifications my invention'may be applied to othercontrol systems usi'rig'fiuid or mechanically operatedelements, andthesignals referred to in the claims may "be 'electricaL'fluid, ormechanical. While I have shown and described a preferred-form of'myinvention, it'is apparent that modifications thereof are possible, andIdo not Wish to be limited to the form shown except as indicated by thefollowing claims:

20 I claim:

1. A directional gyroscope comprising, \a supporting structure, a memberrotatable about a normally vertical axis pivoted therein, a 'rotorhousing pivoted in said member for movement about a normally'horizontalaxis, a rotor in said housing'andhaving a spin-axis perpendicular tothe'axis of said rotor housing, means for applying a torque in reversedirections to said rotatable member, control means actuated by movementof said rotor housing away from that position in which the spin axis ofthe rotor is perpendicular tosaid' vertical axisto control said torqueapplying means to eausereturn'of 'said rotor housing to the position inwhich the spin axis of said rotor is perpendicular to said vertical axisand means to prevent the application "of torque to said member by saidtorque applying means for a period of time after application of spinningpower to said rotor whereby to give said rotor time to come-up to speed.

2. A directional gyroscope comprising, a supporting structure, amember'rotatable about a normally vertical axis pivoted therein, arotorhousing-pivoted in said memberfor movement about a normally'horizontalaxis, arotor in *saidhousing and having a spin axis perpendicular to theaxis of said rotor housing, means for applying a torque in reversedirections to said rotatable member, control means actuated by movementof said rotor housing'away'fromthat positionin which thespin axis-of therotor'is' perpendicular to said vertical axis to-control said torqueapplying means to cause return-of'said rotor housing to the position inwhich the spin axisof said rotor is perpendicular'to said verticalaxisand means to -prevent the application oftorque to said member by saidtorque applying means "until said rotor is spinning at a predetermin'edspeed.

3. 'A directional gyroscope apparatus comprising, a supportingstructure, a member rotatable about a 'normally vertical axis pivotedtherein, a rotor housing pivoted in said member for movement about anormally horizontal axis, stop means for limiting the amount of movementof saidrotor housing"about its axis in each direction a rotor in'saidhousing and having a spin axis perpendicular to the axis ofsaidrotor housing, means for applying a torque in reverse directions to saidmember, relatively movable control means carried by said supportingstructure and said rotatable member and having a desired relativeposition when theapparatusis placed in operation, torque applyingcontrol means operated to control said torque applying means to applytorque to said rotatable'member when said control means is not in thedesired relative position,and'additio'nal means actuated upon return ofsaid control means to the desired position to render said torqueapplying control means inoperative andto thereafter 'maintainthe sameinoperative.

4. A directional gyroscope apparatus comprising, a supporting structure,a member rotatable about a normally vertical axis'pivoted'therein, arotor housing pivoted in said member for movement about a normallyhorizontal axis, stop means for limiting the amount of movement "of saidrotor'housing about its axis in each dir'ection, a'rotor in saidh'ousingand-having-aspin axis perpendicular to the axis of said rotor housing,means forapplying a torque in reverse directions to said member,relatively movable control means carried by said supporting structureand said rotatable-member and having a desired relative position whenthe apparatus is placed in operation, torque applying control meansoperated to control said torque applying means to applytorque to saidrotatable member when said control means isnot in the desired relativeposition,-additional means actuated upon return ofsaid control means tothe desired position to render said torque ap'plying control meansinoperative and to thereafter i maintain the same inoperative, and meansto-prevent th'eapplication of torque to said mem- 21 her by said torqueapplying means for a period of time after application of spinning powerto said rotor whereby to give said rotor time to come up to speed.

5. A centering device for a directional gyroscope having a directionalarm connected thereto to operate a condition responsive element, alocking means adapted to engage said directional arm and prevent itsmovement, and a torque motor adapted to maintain said gyroscope insubstantially horizontal position, said centering device including: arelay adapted to interrupt or restore the normal circuit and operationof said torque motor; switching means to cause said torque motor to turnthe rotor of said gyroscope about a susbtantially vertical axis andthereby center said condition responsive element; and means to operatesaid locking means and simultaneously to operate said relay to restorethe normal circuit and operation of said torque motor.

6. A centering device for a directional gyroscope having a directionalarm connected thereto to operate a condition responsive element, alocking means adapted to engage said directional arm and prevent itsmovement, and a torque motor adapted to maintain said gyroscope insubstantially horizontal position, said centering device including: arelay adapted to interrupt or restore the normal circuit and operationof said torque motor; a wiper operated by said directional arm; a pairof contacts adapted to be selectively engaged by said wiper when saidcondition responsive element is not at the center of its control range,said wiper and said pair of contacts being connected so as to cause saidtorque motor to turn the rotor of said gyroscope about a substantiallyvertical axis and thereby center said condition responsive element; asecond wiper operated by said directional arm; and a contact adapted tobe engaged by said second wiper when said condition responsive elementis at the center of its control range, said second wiper and saidcontact being connected so as to operate said locking means andsimultaneously to operate said relay to restore the normal circuit andoperation of said torque motor.

7. A directional gyroscope which includes: a rotor having asubstantially horizontal spin axis; a cardan ring supporting said rotorand adapted to rotate about a substantially vertical axis; control meansmovable about a substantially vertical axis and connectable to saidcardan ring for operation thereby; a torque motor normally adapted tomaintain the axis of said rotor substantially horizontal; and means tointerrupt the normal operation of said torque motor and to cause it torotate said rotor and said cardan about a substantially vertical axis tocenter said control means with respect to the response range of thelatter.

8. A directional gyroscope which includes: a rotor having asubstantially horizontal spin axis and pivotally mounted for movementabout a substantially horizontal axis substantially perpendicular tosaid spin axis; torque motor means normally adapted to maintain saidspin axis substantially horizontal; and means to prevent theenergization of said torque motor means until said rotor has acquired apredetermined speed.

9. Apparatus for an aircraft having a control surface comprising:operating means adapted to position said control surface, control meansfor said operating means, a gyroscope having a rotor mounted forrotation about a first axis and angularly movable about two respectivelyperpendicular axes which are also perpendicular to said first axis,means for maintaining an angular relation between said first axis andone of said second axes by applying a torque about said third axis,means responsive to relative movements of the gyro and said aircraftabout said third axis and connected to said control means, and meansoperative when the speed of the rotor is below a certain value forrendering inefiective the means for maintaining said angular relation.

10. Control apparatus for an aircraft having a control surfacecomprising: operating means adapted to position said control surface,control means for said operating means, a gyro having an electricallydriven rotor whose impedance varies with the speed thereof and mountedfor movement about three respectively perpendicular axes, means formaintaining an angular relationship be tween said rotor and one of saidaxes, means responsive to relative movement of the aircraft and therotor about another axis and connected to said control means, and meansoperative when the impedance of the rotor is below a certain value forrendering inefiective the means for maintaining said angular relation.

11. Control apparatus for a craft comprising: a gyroscope, a controlmeans having two relatively movable parts one of which may be positionedby said gyroscope and the other by said craft, means operated by saidcontrol means, means for disconnecting said control means and saidoperated means, motor operated means for placing the movable parts in apredetermined position in response to movements of said craft withrespect to said gyroscope, and means for locking said. gyro positionedpart in said predetermined position.

12. Control apparatus for a craft comprising: a gyroscope, meansincluding contacts and a motor for maintaining a predeterminedrelationship between the gyro rotor axis and an axis perpendicularthereto, a control means having a controller comprising two relativelymovable parts one being positioned by the craft the other by saidgyroscope, means operably connected to said control means, means fordisconnecting said control means and said operably connected means, andfurther means adjusted with one of said controller parts fordisassociating said contacts from said motor and for controlling saidmaintaining means so that said relatively movable parts are maintainedin a predetermined relationship.

13. Control apparatus for a craft comprising: a gyroscope, reversiblemotor means for maintaining a predetermined relationship between thegyro rotor axis and an axis perpendicular thereto, a first control.means operative upon the absence of the perpendicular relation forcontrolling said motor means, a second control means for said motormeans responsive to changes in heading of the craft and direction of therotor axis and having two relatively movable parts one being positionedby the craft the other by said gyroscope, operable means connected inseries with said first control means and said motor means for connectingor disconnecting said first control means with said motor means, andmeans including a control element also movable by said gyro upon changesin heading for controlling said operable means for disassociating thefirst control means from its motor means when said gyro axis has movedwith respect to the direction of heading of the craft, whereby said gyroand said craft are maintained in a predetermined relation.

14. In a condition control apparatus having a condition control meanscomprising a three degree of freedom gyroscope sensing changes in saidcondition, said gyroscope having a rotor spinning means therefor, meansapplying a torque to said gyroscope to precess the gyroscope rotor to apredetermined position, means for placing said control means into adesired null condition, and means efiFective on attainment of saiddesired condition by said control means to thereafter energize saidtorque means on departure of the gyroscope rotor from the predeterminedposition.

15. In a condition control apparatus a controller movable relative to asupport therefor, a gyroscope connected to the controller and having arotor spin axis and a second axis perpendicular thereto, means applyinga torque to said gyroscope to cause the rotor to precess about thesecond axis, means including said torque means for placing saidcontroller into a desired position relative to its support, and meansfor rendering said torque means ine'lfective to 'prece'ss theTOtorun'tiI the controller attains such desiredposition.

16. In 'a-control means -for-operating a signal means upon positionaldisagreement ofsaid control means and a support "therefor, a gyroscope'having a spin axis and a precession axis, torque means for said'gyroscope to efiectmovement I thereof about the precession axis, meansresponsive to positional disagreement of said 'control means and supportfor aligning said control means with its support, and means 'forrendering said'torque means ineifective until said control means andsupport are aligned.

-1-7..In a'control means fora craft wherein'said control means developsa control signalupon lack of "positionalagreement of said control meansand 'craft, a gyroscope having torque applying means 'for supplying acouple about a vertical axisof said gyroscope forlevelin'g the rcitortheredfyrotor tilt detecting means for "controlling-said torque means,means 'for controlling-said torque motor in response to positionaldisagreement of said control m'eans and means for transferring controlof said torque means to said tilt detecting means upon said controlmeans attaining positional agreement.

l8. Agyro'scopic control'unit, for anautomatic pilot for aicraft,wherein a rotor has itsspin axismounted in a support, an axis formounting said'support perpendicular to saidspin axis, --a signal deviceresponsive to positional disagreement of the support -axis and thecraft, torque meansfor effecting-rotationof the rotor about the supportaxis, means for initially controlling said torque means from said signalmeans, and means for thereafter controlling said craft from-saidsignalmeans.

19. An aligning arrangement for a gyroscopic positional Control meanshaving a three degreeof freedom gyroscope providing control signals uponangular displacement, comprising spinning means forthe rotor of saidgyroscope, means for applying a torque to said gyroscope for precessingtherotor axis into a predetermined direction, means responsive'tomisalignment'of said control means due to angular displacement ofthegyroscope for primarily operating said torque "means for placingsaid-control means into alignment by reversing said displacement, and'means responsive on attainment'of "the alignment'and ondepartureof'said rotor from its predetermined position to control saidtorque applying means.

-20. The apparatus-o'fclaim 1'9, and means to limit the precession 'of*said rotor While said alignment is 'being effected by reversing thedisplacement of the gyroscope.

2d. In a 'gyroscopic positional control system wherein a gyroscope'hasarotor With a normally horizontal spin axis and a second axisperpendicularthereto, means for applying couples about the second axisfor leveling the gyro spiniaxis m'eansresponsive to displacement from anull 'position about the "second axis 'for controlling a condition, and"means for initially controlling said torque means from said'signal'means to place said control system into the null position.

227 Presetting means for 'a gyroscopic responsive positional con'trolsy-stem-for an aircraft having signal means responsive to positional-misalignment of said craft and gyroscopic rneans, comprising a rotorhaving a spin axis and a precession axis perpendicular thereto, torqueapplying meansforreffectingmotion about the precessionaxis, a circuitfor energi'zing the rotor spinning means, means responsive to the-speedof said rotor and to tilt-of said rotor about its precession-axis forenergizing said torque means.

23. Theiapparatusof claim 22, and further means for preventi'ngl'control'ofsaid torque means by said tilt responsive fmeans until "saidgyroscopic means is placed in alignment with said "craft.

24. A:gyroscopicpositionalcontrol unit for an aircraft comprisingtagyroscope having a rotor, torque means for precessing said rotorymeansresponsiveto tilt-of the rotor axisifor controlling'isaid torque means,means for energizing spinning means for said rotor, and means responsiveto the rotation of said rotor by its spinning means for rendering saidtorque means effective by said tilt responsive means.

References-Cited in the file of this patent UNITED STATES PATENTS BatesJune 6, 1939 Weems Nov. 5, 1946

